Researchers describe a survival strategy in living corals which was only seen in fossil records

Heatwaves in the Mediterranean

According to the authors, some coral colonies that were considered lost years ago show some living parts. Credit: Diego Kersting
According to the authors, some coral colonies that were considered lost years ago show some living parts. Credit: Diego Kersting

University of Barcelona

Some corals can recover after massive mortality episodes caused by the water temperature rise. This survival mechanism in the marine environment -known as rejuvenation- had only been described in some fossil corals so far. A new study published in the journal Science Advances reveals the first scientific evidence of the rejuvenation phenomenon in vivo in Cladocora caespitosa coral colonies, in the marine reserve in Columbrets, in the coast of Castellón (Spain).

The authors of the study are the experts Diego Kersting and Cristina Linares, from the Department of Evolutionary Biology, Ecology and Environmental Sciences from the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the University of Barcelona.

Heatwaves, more and more common in the Mediterranean

The Mediterranean Sea is one of the most affected areas by the climate change and the increase of heatwaves. “We are used to hear and read on the general impacts related to the climate change, but we rarely get news on the life recovery after impacts related to global warming”, says Diego Kersting, first author of the article and researcher at the Free University of Berlin (Germany).

Since 2002, Kersting and Linares have been monitoring 250 coral colonies of Cladocora caespitosa in the marine reserve in Columbrets, an area for studies on the effects of climate change on the marine environment. This coral -the only one able to create reefs in the Mediterranean Sea- is listed as an endangered species, mainly because of the mortalities associated with global warming.

Experts had described that the unusual rise of water temperature in summer was killing many of these Mediterranean coral colonies. For instance, during the summer of 2003, one of the hottest ones, “the 25% of the surface occupied by these corals in Columbrets disappeared due a loss of the colonies”, says the authors of the study.

Some coral polyps survive under extreme conditions

In a Mediterranean Sea with higher and higher temperatures and frequent heatwaves, the survival alarms for these species had already rang. However, the long-run monitoring of the coral in Columbrets revealed a surprising result: some coral colonies that were considered lost years ago show some living parts.

According to the experts, this kind of recuperation was possible thanks to a procedure named rejuvenation. In particular, under stress conditions -for instance, excessive water warming-, some polyps in the coral colonies which are dying are able to become smaller until they can abandon their calcareous skeleton.

In this reduced state, these polyps can survive under extreme conditions which cause the death of the other polyps in the colony. When conditions improve, polyps recover its common size and form a new calcareous skeleton. Afterwards, they reproduce by budding until they can recover the dead colony again.

A hidden survival strategy

According to the authors, this survival strategy had been unnoticed until now due the external good image the colonies show once they have recovered, which masks the mortality that had taken place before. “The real story of these colonies can only be found if controlled every year, over the years, or if we study the skeleton, since the process leaves characteristic features!, warn Kersting and Linares.

So far, researchers had found signs of this rejuvenation only in Paleozoic corals, which lived hundreds of millions of years ago. Therefore, the results of this study will enable making comparisons between the in vivo observations and the description through the fossils, and therefore knowing the implication of these kinds of survival processes and adaptation in corals.

This discovery provides new perspectives for the survival of the only reef coral in the Mediterranean, which has a slow growth -about 3 mm per year- and a limited ability to create new colonies. “However, it is hard for these mechanisms to balance the serious increase of the frequency and severity of the heatwaves in the Mediterranean, so it is necessary to act urgently in order to slow the causes of climate change, and dedicate enough resources to maintain these monitoring procedures in the long run”, warn the authors.


From EurekAlert!

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October 19, 2019 6:15 am

So our fossil fuel emissions are not doing in the coral reefs after all?

Reply to  chaamjamal
October 19, 2019 6:26 am

Nor is the changing climate.

Good news, I’d say.

Charles Higley
Reply to  chaamjamal
October 19, 2019 8:45 am

It seems, as many innocent scientists do, that these researchers assume that global warming by man is real and then interpret anything that happens as an effect. They offer no data regarding increased heatwaves. Why not? Have they even looked? They simply monitor the corals and assume that a heatwave must have occurred when there is a coral die-off. There is nothing else can can cause a die-off?It’s backward thinking and false science not to gauge everything involved in your thesis.

Reply to  Charles Higley
October 19, 2019 1:22 pm

Backward thinking indeed. But this is how an alarmist would read the paper:

bla bla bla necessary to act urgently in order to slow the causes of climate change bla“.

Kristi Silber
Reply to  Charles Higley
October 20, 2019 8:19 pm


It’s not assumption. Most scientists believe that AGW is real because there is so much evidence for it, and so don’t feel it necessary to justify their beliefs in every paper they write. That certainly doesn’t mean they “interpret everything that happens as an effect,” but when there are demonstrable correlations between temperature and coral die-off, which has been shown all over the world, and when the physiological mechanism is known, it’s hard to argue that some mysterious unknown cause it at play. If you have another explanation, do the research and write it up.

It seems to be you who are making assumptions. The temperature data are available. A description of the methods is in another study, which they cited.
“The SST data have been recorded daily in the Columbretes Islands Marine Reserve since 1991 at depths of 1 m using a calibrated mercury-in-glass thermometer (Thies Clima, model 2.2141.00.64, Göttingen, Germany). The temperature was measured between 8:00 and 9:00 a.m. by the Marine Reserve wardens following the same protocol (bucket sampling in the first meter of water and direct measurement with the thermometer). Overall, 6,028 daily measurements of SST were collected, which covers 75% of the 1991–2012 period, with a mean value of 274 data logs per year and a mean temporal cover of 87% during the summer (June-September).”

It’s easy to make accusations of false science when you don’t understand the science to begin with, or take into account your own biases. And calling it “assumption” to accept AGW as reality makes sense only if you don’t understand the basis of the theory or know all the evidence supporting it.

October 19, 2019 7:00 am

Corals thrive in the hottest sea of the planet — the Red Sea. ‘Nuff said.

Reply to  beng135
October 19, 2019 8:06 am

Exactly. Not only have I witnessed this in my aquarium, temperature is much less of a stressor than changes in alkalinity or turbidity. This would be an excellent article if they didn’t contort their conclusions to fit the CAGW narrative.

Curious George
Reply to  beng135
October 19, 2019 9:44 am

How do you observe rejuvenation in fossil corals?

Reply to  Curious George
October 19, 2019 12:43 pm

I suppose by way of detailed examinations of fossil Paleozoic corals. A link might have been handy.

Kristi Silber
Reply to  ontherocks
October 20, 2019 8:36 pm


Link to the paper discussed: From there, you can find research related to fossil corals.

Reply to  Curious George
October 20, 2019 7:40 am

Exactly Curious George!

Just how do researchers study rejuvenation in fossil corals. Corals that are one miniscule slice of time over a million years?
Unless, they are a research team that leaps to assumptions. Global warming, Mediterranean warming, all caused by people.

Apparently not one of these researchers has bothered to research how corals have survived during the Holocene with warming seas and sea level rising hundreds of meter…

Twits. Every one of them.

Kristi Silber
Reply to  ATheoK
October 20, 2019 8:32 pm


Or maybe, rather than making assumptions, there’s a whole research literature on these subjects that they can refer to. Maybe it’s just YOU who doesn’t know about the research that has been done, so make erroneous assumptions and false accusations. In that case, who’s the real twit?

October 19, 2019 7:24 am

You mean to tell me Peter Ridd was right all along?
Better message the sad sacks at James Cook University with the good news as it sounds like they all need a bit of cheering up and jollying along.

October 19, 2019 7:51 am

According to the experts, this kind of recuperation was possible thanks to a procedure named rejuvenation.

That’s like saying I got better because I recovered.

Reply to  commieBob
October 19, 2019 8:19 am

Cheers to your recovery.

Reply to  commieBob
October 19, 2019 9:40 am

Not exactly, they are theorizing a previously unknown phenomena wherein the coral polyps abandon their skeletons and become freely drifting “climate change refugees” until such a time that they can reestablish themselves in a better location. …interesting.
Freely floating coral polyps are essentially what get created during coral breeding. How did the researchers determine the newly created refugee polyps from floating polyps cause by fertilization in these measurement zones? Could it simply be that the “rejuvenation” is merely reestablishment by coral polyps from other areas. Sounds a bit similar to “Spontaneous Generation”, …and that didn’t turn out to be correct.

Jean Parisot
Reply to  Rocketscientist
October 19, 2019 11:47 am

Many species change reproductive strategies in response to pressure. That coral, which has survived millenniums and wide ranges of conditions has mechanisms to recover and rejuvenate should not be controversial.

October 19, 2019 8:10 am

“However, it is hard for these mechanisms to balance the serious increase of the frequency and severity of the heatwaves in the Mediterranean, so it is necessary to act urgently in order to slow the causes of climate change, and dedicate enough resources to maintain these monitoring procedures in the long run”, warn the authors.

“Therefore, we need more funding.” was left off.

Reply to  fish
October 19, 2019 8:40 am

It’s implicit.

Reply to  fish
October 20, 2019 8:27 am

Maybe during a heatwave the surface temperature can go up for some days but not the bulk of water under the surface where the coral lives.
Long winter cold periods would be a bigger stress for corals.

October 19, 2019 9:41 am

“Since our “coral extinction due to CAGW” fraud has been exposed (thanks to Peter Ridd),
we now have to invent a new ugly canard to explain why corals are just fine :
– Hey ! They are fine because they suddenly adapted to CAGW ! Problem solved !”

BTW, we are sure that EurekAlert will publish our BS,
because the climate clown show must go on !

Mike O
October 19, 2019 10:04 am

A couple of things. It is interesting that the coral grows at the same rate as the sea level rise. Coincidence?

Also, one good thing about the Climate Change scare is that we are focusing more scientific research dollars on the problem and continually showing how resilient the earth’s eco-systems are.

Climate changes and will always continue to do so, but our planet endures.

Reply to  Mike O
October 19, 2019 10:36 am

It’s a damn good thing coral can’t grow above sea level . 🙂

Reply to  Rocketscientist
October 19, 2019 3:28 pm

Egads maybe the corals will climb out of the water if the seas get too hot? Needs more grants to study this new climate change threat.

October 19, 2019 10:21 am

“The Mediterranean Sea is one of the most affected areas by the climate change”

It appears that everybody’s area of study is the one most affected by climate change.

Reply to  BillP
October 19, 2019 1:05 pm

Well, there is validity in your comment. But the area is somewhat unique as we (apparently) haven’t another example of a basin-wide event as the Miocene-age “Messinian Salinity Crisis” that caused significant desiccation of most (or all) of the Mediterranean for 600,000 years. (That qualifies as a major change in climate, caused by Plate Tectonics”.)

After Table 1, there is a good description of the “Mid-Latitude High-Pressure Zone” and its effects on the region.

Reply to  ontherocks
October 19, 2019 1:17 pm

The Zanclean Flood, which refilled the Mediterranean, must have been pretty wild.

Reply to  BillP
October 19, 2019 1:06 pm

Yep. Everywhere it’s worse than we thought.
comment image

Reply to  BillP
October 19, 2019 1:41 pm

I would imagine it’s warming at twice the global average, just like everywhere else.

J Mac
October 19, 2019 3:41 pm

Coral survival strategy? How about “Leave ’em the hell alone!” They’ll figure it out, like they’ve been doing for the last 500,000,000 years or so!

Robert B
October 19, 2019 3:58 pm

You have to wonder why they evolved this way if hratwaves in the Mediterranean were unprecedented.

October 19, 2019 4:19 pm

If Corals grow well in the Red Sea, them its not water temperature e, bunt the different creatures who use the basic coral to build on.

If Global warming is a problem in one place, then it should affect all Coral.

Has any transplanting taken place, some from the Red Sea being placed on reefs elsewhere ?


Reply to  Michael
October 20, 2019 12:37 pm

This is a COLD WATER coral. Hermatypic (reef-building) corals became extinct in the Mediterranean during glaciations and haven’t been able to recolonize.

Introducing Red Sea corals wiuld probably work in the Eastern Mediterranean, the Western Mediterranean is almost certainly too cold.

wayne job
October 20, 2019 12:15 am

In Oz we have the climate worriers that tell us the great barrier reef is doomed, this reef is about 1000km long.
Out further a reef in deeper water was found much to the surprise of the worriers. Bleaching has occurred in parts because of odd tides that left bits exposed.

These are recovering fast, what these worriers fail to realise is that the oceans have gone up and down in the past and a lot of the beaches are made of old coral!!

October 20, 2019 5:49 am

With regards to corals this is about as factually incorrect as it can be.

Most of the Mediterranean is too cold for hermatypic (reef-building) corals. The southeastern part is warm enough, but hermatypic corals there became extinct during the Pleistocene glaciations. It has not been recolonized because coral larvae can’t survive the long transit through Gibraltar sound and the cold upwelling areas off Morocco.

Since the Suez canal was built a lot of “lessepsian colonizers” have reached the eastern Mediterranean from the Red Sea by way of the canal, but hermatypic corals and coral larvae seem unable to do it, probably both because the shallow water in the canal is too cold in winter (15 C) and there is also too much turbidity due to the heavy traffic.

Incidentally most of those colonizers are really “re-colonizers” that lived in the Mediterranean before the Pleistocene Ice Ages.

October 20, 2019 9:40 am

Ring Rang Rung
He rings the bell, He rang the bell, He has rung the bell
past tense- He had rung the bell.

Either the spell checker is faulty, or well-educated professors and editors don’t know how to proof read.

Just as in climate models, little mistakes can build urp imto unreduble txtx.

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